Seatbelt retractor

Abstract

A mounting concave portion with a predetermined depth is formed on a gas-pressure-receiving-side surface of a piston. Further, a plate-like sealing member includes a mounting convex portion which is erected at a position meeting with the mounting concave portion on the gas-pressure-receiving-side surface of the piston. When the piston and the sealing plate are assembled together, the mounting convex portion is fitted in the mounting concave portion. By merely pushing the mounting convex portion in the mounting concave portion, the sealing plate and the piston can be integrated, which improves productivity in assembly. Further, the sealing plate will not get twisted, deviated or displaced due to friction against inner wall of the pipe cylinder when the sealing plate and the piston are integrally inserted in the pipe cylinder. Deterioration of sealing function due to improper mounting of the sealing plate can be avoided.

The invention claimed is: 
     
       1. A seatbelt retractor comprising:
 a housing; 
 a take-up drum that is rotatably supported at the housing and urged in a webbing-take-up direction while a webbing is wound therearound; and 
 a pretensioner mechanism that forces the take-up drum to rotate in the webbing-take-up direction in case of vehicle collision and takes up the webbing in the take-up drum, 
 wherein the pretensioner mechanism comprises: 
 a gas generating member that generates gas; 
 a cylinder that is long and coupled with the gas generating member; 
 a pinion gear body that is capable of rotating integrally with the take-up drum; 
 a piston that is housed in the cylinder in a movable manner, pressed and driven by pressure of the gas, equipped with a rack getting engaged with the pinion gear body at a side surface portion thereof, and forced to rotate the take-up drum in the webbing-take-up direction via the pinion gear body when pressed and driven; and 
 a sealing member that is a plate-like member having elasticity and a substantially similar shape with a gas-pressure-receiving-side surface of the piston, and mounted to the gas-pressure-receiving-side surface of the piston so as to seal a space between the piston and an inner wall of the cylinder, 
 wherein the piston includes: 
 a mounting concave portion having a predetermined depth at the gas-pressure-receiving-side surface thereof; and 
 a communicating hole that is configured to perforate through the piston along a movement direction of the piston from the mounting concave portion, 
 wherein the sealing member includes a mounting convex portion erected at a position that meets with the mounting concave portion, and 
 wherein the sealing member is mounted to the piston with the mounting convex portion being press-fitted to the mounting concave portion, and configured so that the gas flows into the communicating hole from the mounting convex portion when the piston is pressed and driven by pressure of the gas. 
 
     
     
       2. The seatbelt retractor according to  claim 1 , wherein the sealing member includes a gas receiving peripheral portion which is formed to protrude at an entire peripheral portion thereof by a predetermined height toward a side of the gas generating member. 
     
     
       3. The seatbelt retractor according to  claim 2 , wherein the sealing member includes a piston buffer portion which protrudes at an entire peripheral portion thereof by a predetermined depth toward the gas-pressure-receiving-side surface of the piston. 
     
     
       4. The seatbelt retractor according to  claim 1 , wherein
 the sealing member includes a gas releasing hole that is configured to perforate through the mounting convex portion in a thickness direction thereof. 
 
     
     
       5. The seatbelt retractor according to  claim 1 , wherein
 the piston includes a positioning concave portion which has a predetermined depth at the gas-pressure-receiving side surface thereof, 
 the sealing member includes a positioning convex portion at a position that meets with the positioning concave portion, and 
 the positioning convex portion of the sealing member is inserted in the positioning concave portion of the piston. 
 
     
     
       6. The seatbelt retractor according to  claim 1 , wherein
 the sealing member includes a fragile portion which is formed to cover the communicating hole of the piston in the mounting convex portion from a surface opposite to a surface facing the gas-pressure-receiving-side surface of the piston, and 
 the fragile portion is fractured by the gas and perforated by the mounting convex portion. 
 
     
     
       7. The seatbelt retractor according to  claim 1 , wherein
 the sealing member includes a gas releasing hole that is configured to perforate through the mounting convex portion in a thickness direction thereof, and 
 the gas releasing hole melts and widens hole diameter thereof due to the gas. 
 
     
     
       8. The seatbelt retractor according to  claim 7 , wherein the gas releasing hole is formed so that a center thereof is offset with reference to a position of the communicating hole of the piston.